1. Field of the Invention
The present invention relates to a nitride semiconductor laser device, and particularly to a nitride semiconductor laser device having a characteristic in an atmosphere within a cap in which a nitride semiconductor laser element is enclosed.
2. Description of the Background Art
A conventional semiconductor laser device that can be installed in a vacuum environment or high-pressure environment is disclosed in Japanese Patent Laying-Open No. 10-313147. Details of the disclosed semiconductor laser device are as follows. Referring to FIG. 4, a semiconductor laser source disclosed in Japanese Patent Laying-Open No. 10-313147 includes such components as a semiconductor laser chip 41 emitting a laser beam, a heat sink 42 having its end on which semiconductor laser chip 41 is provided, a stem 43 to which the bottom surface of heat sink 42 is joined, and a light detecting element 44 placed on a surface of stem 43 for monitoring the intensity of the laser beam emitted from semiconductor laser chip 41. On the opposite surface of stem 43, electrode leads 47 respectively for grounding, for driving the semiconductor laser and for the light detecting element are attached. The ground electrode is joined to the stem and rendered electrically conductive, and the electrode for driving the semiconductor laser and the electrode for the light detecting element are joined respectively to semiconductor laser chip 4 and light detecting element 44 by wire bonding (not shown) and rendered electrically conductive.
The semiconductor laser source as shown in FIG. 4 is structured by molding all of semiconductor laser chip 41, heat sink 42, light detecting element 44 and stem 43 except for electrode leads 47, using a light-transmitting plastic material 49 such as synthetic resin. It is disclosed in the aforementioned publication that the packaging in this form allows semiconductor laser chip 41 to be installed in a vacuum environment or high-pressure environment since this form of packaging has no parts like cap and cover glass that lack strength.
Japanese Patent Laying-Open No. 10-313147 also discloses that the internal atmosphere enclosed in a cap made of the light-transmitting plastic material is an inert gas atmosphere, and accordingly the semiconductor laser device can be installed in a vacuum environment or high-pressure environment.
If the semiconductor laser device in the aforementioned publication uses a nitride semiconductor laser element as the semiconductor laser element, an end surface of a resonator (hereinafter “resonator end surface”) of the laser element will be blackened. The blackening results in a problem of deterioration in output light intensity of the nitride semiconductor laser element or shortening of the lifetime thereof.